In order to reduce the assembly cost during the assembly of an internal combustion engine of a motor vehicle and reduce the warehousing and logistics costs during the engine assembly process, the suppliers deliver already fully assembled engine modules directly to the assembly line of the automobile makers. Such engine modules consist, e.g., of a cylinder head cover module with one or more camshafts mounted therein. Then only this cylinder head module is fastened to the cylinder head of the engine during the engine assembly process.
From DE 10 2010 045 047 A1 for example there is known a method for assembly of a module for a motor vehicle engine with at least one cylinder head cover module and a camshaft mounted therein.
Camshafts in cylinder head cover modules are usually subjected to relatively high stresses, especially bending stresses, and forces during operation of the internal combustion engine. Thus a need exists to improve cylinder head cover modules so that the camshaft can withstand such high stresses, bending stresses, and forces.
The cylinder head cover module has a cover body and a camshaft arranged therein. The cover body has an opening, in which a bearing element is press-fitted. The camshaft is rotatably mounted in the bearing element, preferably at one of its ends. The bearing element seals off the opening of the cover body from the exterior. In particular, the opening is sealed off in an oil-tight and/or water-tight manner by the bearing element. Of course, the cover body may also have several of such openings, in each of which a bearing element of this kind is press-fitted.
In this context, the term “cylinder head cover module” should be understood to mean an assembled component, which can be arranged on a cylinder head of an internal combustion engine. By the term “cover body” is meant a base body of the cylinder head cover module, in which further elements such as the camshaft are introduced and secured during the manufacturing process of the cylinder head cover module. The cover body may be cast or injection molded, for example from plastic.
The cylinder head cover module may comprise expedient elements, such as further bearings, in which the camshaft is rotatably mounted. The camshaft expediently comprises a pipe or a support shaft, on which multiple cams are arranged. Besides the cams, further components may also be arranged on the support shaft, such as a camshaft encoder wheel for adjusting an angle of rotation of the camshaft and/or a pump cam for driving a fuel and/or injection pump.
Of course, the cylinder head cover module may also have several camshafts. A bearing element may be press-fitted into a corresponding opening in the sense of the invention for several or all of these camshafts.
In the course of the method for producing such a cylinder head cover module, the camshaft is introduced into the cover body and in particular oriented and secured in the cover body. The bearing element is press-fitted into the opening of the cover body such that the camshaft is rotatably mounted in the bearing element, especially on one of its ends, and the bearing element seals off the opening of the cover body from the exterior. The opening of the cover body serves in particular for guiding or precisely orienting the camshaft during the manufacturing process of the cylinder head cover module, for example by means of a so-called centering or guiding lance, as further explained below.
In traditional cylinder head cover modules, the opening is closed after the camshaft has been oriented and secured, for example by means of a closing cover, which is merely inserted into the opening. The corresponding end of the camshaft is therefore not mounted, but rather freely suspended in the air. In such traditional cylinder head cover modules it is a disadvantage that the camshaft cannot withstand any comparatively large stresses or bending stresses at this end. If the camshaft in such traditional cylinder head cover modules needs to be subjected to relatively large forces or stresses, a further bearing is screwed into the cover module or the last bearing is greatly lengthened, which may result in a lengthening of the overall cylinder head cover module and an increased weight, as well as increased design space. Also, it usually cannot be ensured by the inserting of a closing cover that the cylinder head cover module is tightly closed or sealed off from the exterior.
By contrast, in a cylinder head cover module according to the invention, the inexpensive press fitting of the bearing element in the manufacturing process accomplishes better qualities and advantages. An improved mounting of the camshaft can be assured, so that the camshaft can withstand more force and be subjected to greater stresses. At the same time, the cylinder head cover module is sealed off from the exterior. Thanks to this press fit between bearing element and cylinder head cover module and the corresponding force locking connection, these two elements are tightly sealed off against each other, so that no fluids, especially no oil and/or water, and no foreign bodies can get into the cylinder head cover module. Furthermore, this force locking connection is not easy to loosen.
Advantageously, the bearing element comprises a plain bearing for rotatable mounting of the camshaft. The interior of the bearing element is expediently bored out and adjusted to the dimensions of the plain bearing. Such a plain bearing is especially suited to the mounting of the camshaft, since the sliding friction and the corresponding sliding resistance can be kept low and the heat generated can be effectively dissipated. In particular, the camshaft can be especially effectively mounted by the use of a lubricating fluid, such as an appropriate oil. Emergence of the lubricating fluid is prevented by the oil-tight and force locking connection to the cylinder head cover module.
Preferably the bearing element comprises a port for supplying the plain bearing with a lubricating fluid. For this purpose, the bearing element is oriented in particular or press-fitted with corresponding orientation in the course of the manufacturing process.
Preferably the bearing element has a closure surface, which fits together with the cover body. If the bearing element is pressed into the cover body, the opening is in particular closed by said closure surface, so that the cover body has an enclosed shell surface. According to an especially preferred embodiment, the bearing element is designed as a plain bearing block, an opening of the plain bearing being situated on one side of this plain bearing block, into which opening the end of the camshaft is introduced. On the side opposite this opening, the plain bearing block has the closure surface in particular, which fits together with the cover body and seals it off. In particular, the plain bearing and the closed surface are situated with a certain spacing from each other in the plain bearing block.
The bearing element is preferably made at least partly of aluminum. In this way, the bearing element can have a light, compact, stable and economical construction. The use of another expedient material, such as plastic, is likewise conceivable.
According to one advantageous embodiment, the camshaft comprises a pump cam at one end or in the vicinity of the end. This pump cam serves in particular for actuating a fuel and/or injection pump. Such a fuel pump is provided in particular for delivering fuel from a fuel tank to injection valves or the injection pump of the internal combustion engine. By means of such an injection pump, fuel is delivered expediently under high pressure through the injection valves into the combustion chamber of the cylinder or the intake pipe. By arranging such a pump cam at the end of the camshaft a relatively large bending stress is produced, which can be effectively compensated by the bearing element. Of course, other expedient components may also be arranged at the end of the camshaft, such as a camshaft encoder wheel.
Advantageously the camshaft is inserted into the cover body by introducing a support shaft and components connected to the support shaft, especially cams as well as pump cams and/or a camshaft encoder wheel, into the cover body and connecting them with each other in the cover body. The camshaft thus has a modular design and the individual modular elements of the camshaft are assembled only in the course of the manufacturing process of the cylinder head cover module. The cylinder head cover module can thus be manufactured in an especially simple and flexible manner.
Advantageously the support shaft of the camshaft is introduced through the opening or through a second opposite opening into the cover body during the manufacturing process. A further bearing can be arranged in this second opening, such as a plain bearing, through which the support shaft is introduced into the cover body. As already explained, the support shaft or the assembled camshaft can be led through the opening and/or also through the second opening, for example by means of a centering or guiding lance. In this way, the camshaft can be led precisely through the opening or openings during the manufacturing process and the opening can be closed tightly by means of the bearing element after the securing of the camshaft.
According to one preferred embodiment, the cylinder head cover module is produced by means of the so-called Presta2 method developed by the applicant. A detailed description of such a method is disclosed for example in DE 10 2010 045 047 A1.
Preferably the components connecting to the support shaft are at first arranged in the cover body. The components expediently have passage openings, through which the support shaft can be led. In particular, the components are arranged in the cover body such that their passage openings are aligned with the opening in the cover body. For this purpose, a guiding or centering lance can be used, in particular.
Advantageously the support shaft is cooled, for example by means of liquid nitrogen. The cover body and the components connected to the support shaft are at first heated. For example, the support shaft may be cooled down to temperatures of as low as −200° C., the components may be heated up to temperatures of as much as +200° C. and the cover body in particular to temperatures between 45° C. and 65° C. The support shaft thus contracts and its diameter becomes smaller. The components and the cover body expand in this process.
The cooled support shaft is preferably introduced into the heated cover body and led preferably through the passage openings in the heated components. In particular, the support shaft is introduced through the opening in the cover body or through the second opening. For example, the support shaft may be designed hollow on the inside and it may be pushed across the centering lance. The cooled and contracted support shaft can be led especially easily into the expanded cover body and through the expanded components.
The support shaft is thereupon preferably heated and the components and the cover body are preferably cooled. This heating and cooling may occur actively, but an automatic temperature equalization may also occur, waiting until the support shaft, cover body and components have reached room temperature. The support shaft may then be oriented precisely in the cover body, especially through the opening by means of centering lances, and likewise the components can be oriented relative to the support shaft. After this, the components can be firmly connected to the support shaft, for example, by press fitting the components onto the support shaft.
Preferably the bearing element is thereupon press fitted into the opening such that the camshaft is rotatably mounted in the bearing element and the bearing element seals off the opening of the cover body from the exterior. The bearing element may also be press-fitted into the opening at an earlier time in the manufacturing process. For example, the bearing element may also be press-fitted into the opening at the start of the manufacturing process. After this, the components are arranged in the cover body, and the cover body and components are heated. The support shaft is cooled, introduced through the second opening into the cover body, and led through the passage openings and into the bearing element. After this, the cover body and components are cooled, and the support shaft is heated.
Further benefits and embodiments of the invention will emerge from the description and the accompanying drawing.
Of course, the features mentioned above and yet to be further explained below may be used not only in the particular indicated combination, but also in other combinations or standing alone, without leaving the scope of the present invention.
The invention is represented schematically with the aid of an exemplary embodiment in the drawing, and it shall be described below with reference to the drawing.